Conservation of blood during cardiovascular surgery

Consensus of the Brazilian association of hematology, hemotherapy and cellular therapy on patient blood management: Definition of Patient Blood Management

Managing the patient's blood and hematopoietic system is like managing any of the other organs and organ systems during patient care. Specialists control the heart, kidneys, endocrine system, etc. and the patient's blood requires similar clinical treatment. The hematopoietic system and its circulatory products are fundamental for the healthy functioning of the human body. In simple terms, Patient Blood Management (PBM) is an organized, patient-centered approach in which the entire healthcare team coordinates efforts to improve outcomes by managing and preserving the patient's own blood. By reducing dependence on blood transfusions, PBM seeks to improve clinical outcomes, reduce the risks and costs associated with transfusions, and improve the safety and quality of patient care. Essentially, the concept of PBM is about the holistic management and preservation of the patient's own blood in the medical and surgical context.

A Global Definition of Patient Blood Management

While patient blood management (PBM) initiatives are increasingly adopted across the globe as part of standard of care, there is need for a clear and widely accepted definition of PBM. To address this, an expert group representing PBM organizations, from the International Foundation for Patient Blood Management (IFPBM), the Network for the Advancement of Patient Blood Management, Haemostasis and Thrombosis (NATA), the Society for the Advancement of Patient Blood Management (SABM), the Western Australia Patient Blood Management (WAPBM) Group, and OnTrac (Ontario Nurse Transfusion Coordinators) convened and developed this definition: "Patient blood management is a patient-centered, systematic, evidence-based approach to improve patient outcomes by managing and preserving a patient's own blood, while promoting patient safety and empowerment." The definition emphasizes the critical role of informed choice. PBM involves the timely, multidisciplinary application of evidence-based medical and surgical concepts aimed at screening for, diagnosing and appropriately treating anemia, minimizing surgical, procedural, and iatrogenic blood losses, managing coagulopathic bleeding throughout the care and supporting the patient while appropriate treatment is initiated. We believe that having a common definition for PBM will assist all those involved including PBM organizations, hospital administrators, individual clinicians and policy makers to focus on the appropriate issues when discussing and implementing PBM. The proposed definition is expected to continue to evolve, making this endeavor a work in progress.

LA TRASFUSIONE DI SANGUE NELLA CHIRURGIA ONCOLOGICA: RUOLO DELLA ERITROPOIETINA RICOMBINANTE UMANA (rHuEPO)

Anemia is common in cancer patients. The pathophysiology is multifactorial, however the most common cause is the anemia of chronic diseases (ACD). In 20-50% of cancer patients, anemia restricts physical activity and quality of life and requires transfusion support. The percentage of patients necessitating transfusion dramatically increases when patients require surgery.

The traditional belief that blood transfusion is an effective and safe therapy has been challenged by a heightened awareness of the infectious and immunologic risks associated with allogeneic blood administration. In cancer patients transfusion-induced immunomodulation may have the potential to significantly increase postoperative infections and cancer recurrence so that it seems reasonable to minimize allogeneic blood exposure.

Several strategies have been adopted to reduce allogeneic transfusion in surgical patients, however to properly select the appropriate blood conservation strategies the blood transfusion requirements for each patient should be defined.

Allogeneic blood transfusion in surgery can be reduced by the introduction of autologous blood (AB) programmes and by the use of rHuEPO, alone or in association with AB techniques. AB donation is currently a standard of care for elective surgical patients but its efficacy is limited by anemia that prevents the donation of the optimal number of AB units. rHuEPO has been shown to significantly increase the volume of AB that anemic patients can predeposit or, used perisurgically, to expand the circulating RBCs mass before surgery. Moreover clinical trials employed rHuEPO in anemic cancer patients with various solid tumors both on and off chemotherapy reporting a significantly increase in Hct in more than 50% of the treated patients. Recently different studies have shown the efficacy of rHuEPO in increasing the volume of AB also in patients with ACD and cancer, thus proving to be a useful addition to existing strategies of blood conservation to minimize exposure to allogeneic blood in surgical cancer patients.

Development and validation of Transfusion Risk Understanding Scoring Tool (TRUST) to stratify cardiac surgery patients according to their blood transfusion needs

BACKGROUND

Allogeneic blood transfusion is associated with transfusion reactions, infection transmission, and postoperative morbidity and mortality. The objective of this study was to develop and validate an accurate and simple clinical index to stratify cardiac surgery patients according to their blood transfusion needs.

METHODS AND RESULTS

Data on consecutive adult patients who underwent cardiac surgery at Toronto General Hospital (n = 11,113) and Sunnybrook and Women's College Health Sciences Center (n = 5316) between May 1999 and June 2004 were collected for the development, validation, and external validation of the index. Primary outcome was the exposure to blood transfusion in the operative and first postoperative days. Multivariable logistic regression modeling techniques were used to determine the relationship between each independent variable and the exposure to allogeneic blood transfusion. Score assignment for each predictor variable was based on its regression coefficient. The predicted probabilities at each total score were compared to the observed proportions of patients exposed to blood transfusion. The clinical tool consists of eight preoperative variables: preoperative hemoglobin, weight, female sex, age, nonelective procedure, preoperative creatinine, previous cardiac surgical procedure, and nonisolated procedure.

CONCLUSIONS

Based on the standards of measurement in clinical research, a valid clinical tool was developed for predicting the need for blood transfusion in patients undergoing cardiac surgery. The clinical tool was internally and externally validated, and the results suggest that it should perform well at other institutions.

Critical values of hematocrit and mixed venous oxygen saturation as parameters for a safe cardiopulmonary bypass

OBJECTIVE

Mixed venous oxygen saturation (SvO2) is high despite a low hematocrit implies that the relationship between oxygen demand and supply is in a safe state. This study was sought to determine the critical values for hematocrit and SvO2 for safe cardiopulmonary bypass.

METHODS

Study 1: To evaluate the limit of hemodilution without cardiopulmonary bypass, normovolemic hemodilution with Dextran 40 (10%) was performed in 14 rabbits. SvO2 was monitored from the right atrium, and the hemodynamic parameters were recorded continuously. Study 2: To determine the critical values for hematocrit and SvO2 during cardiopulmonary bypass, normothermic and hypothermic cardiopulmonary bypass were performed in 13 rabbits and hemodynamic parameters were corrected.

RESULTS

Study 1: The heart rate decreased to unsafe levels abruptly, when the SvO2 was < or = 43% or the hematocrit was < or = 10%. The lactate concentration increased when the SvO2 was < or = 46% or the hematocrit was < or = 12%. Study 2: When the hematocrit was < or = 12%, the SvO2 decreased gradually. Even when weaning was possible, the animals with a hematocrit < or = 12% collapsed hemodynamically within 40 minutes after cardiopulmonary bypass. Most of the animals could not be weaned from cardiopulmonary bypass during either normothermic or hypothermic cardiopulmonary bypass when the SvO2 was < or = 46%.

CONCLUSIONS

Continuous monitoring of hematocrit and SvO2 provides evidence-based guidelines for safe cardiopulmonary bypass. The lower limits of critical range for a safer cardiopulmonary bypass are hematocrit of 12% and SvO2 of 46%.

Post-operative course of coronary artery bypass surgery patients who pre-donate autologous blood

BACKGROUND

Pre-operative autologous blood donation is used to reduce the need of allogeneic blood in patients undergoing coronary bypass surgery operations, but it is not clear what impact the blood donation has on the post-operative course of these patients.

METHODS

We studied the post-operative course of 210 patients who pre-donated autologous blood before their coronary bypass operation (donors) and of 67 patients who were eligible to pre-donate but did not (controls).

RESULTS

The clinical variables and the technical operative parameters of the patients in the two groups were similar. There was no significant difference between the duration of assisted ventilation post-operatively (756 +/- 197 vs. 802 +/- 395 min; P=0.54) or length of stay in the intensive care unit (1.8 +/- 1.1 vs. 1.7 +/- 0.9 days; P=0.52) of the two groups. The number of autologous units of packed red cells and of fresh frozen plasma (FFP) received by the donors was significantly higher than the number of units of allogeneic packed red cells (1.5 +/- 0.9 vs. 0.3 +/- 0.9; P=0.001) and the units of homologous FFP received by the controls (2.3 +/- 0.8 vs. 0.6 +/- 1; P=0.001).

CONCLUSIONS

We found no evidence that autologous blood donation exerted a negative influence on the post-operative course of patients undergoing coronary bypass surgery. Patients who pre-donated blood received no allogeneic blood products, but the number of autologous blood products received by donors was higher than the number of blood products received by patients who did not pre-donate.

Factors affecting transfusion of fresh frozen plasma, platelets, and red blood cells during elective coronary artery bypass graft surgery

CONTEXT

The ability to predict the use of blood components during surgery will improve the blood bank's ability to provide efficient service.

OBJECTIVE

Develop prediction models using preoperative risk factors to assess blood component usage during elective coronary artery bypass graft surgery (CABG).

DESIGN

Eighty-three preoperative, multidimensional risk variables were evaluated for patients undergoing elective CABG-only surgery.

MAIN OUTCOMES MEASURES

The study endpoints included transfusion of fresh frozen plasma (FFP), platelets, and red blood cells (RBC). Multivariate logistic regression models were built to assess the predictors related to each of these endpoints.

SETTING

Department of Veterans Affairs (VA) health care system.

PATIENTS

Records for 3034 patients undergoing elective CABG-only procedures; 1033 patients received a blood component transfusion during CABG.

RESULTS

Previous heart surgery and decreased ejection fraction were significant predictors of transfusion for all blood components. Platelet count was predictive of platelet transfusion and FFP utilization. Baseline hemoglobin was a predictive factor for more than 2 units of RBC. Some significant hospital variation was noted beyond that predicted by patient risk factors alone.

CONCLUSIONS

Prediction models based on preoperative variables may facilitate blood component management for patients undergoing elective CABG. Algorithms are available to predict transfusion resources to assist blood banks in improving responsiveness to clinical needs. Predictors for use of each blood component may be identified prior to elective CABG for VA patients.

The theory and practice of bloodless surgery

The application of blood conservation strategies to minimise or avoid allogeneic blood transfusion is seen internationally as a desirable objective. Bloodless surgery is a relatively new practice that facilitates that goal. However, the concept is either poorly understood or evokes negative connotations. Bloodless surgery is a term that has evolved in the medical literature to refer to a peri-operative team approach to avoid allogeneic transfusion and improve patient outcomes. Starting as an advocacy in the early 1960s, it has now grown into a serious practice being embraced by internationally respected clinicians and institutions. Central to its success is a coordinated multidisciplinary approach. It encompasses the peri-operative period with surgeons, anaesthetists, haematologists, intensivists, pathologists, transfusion specialists, pharmacists, technicians, and operating room and ward nurses utilising combinations of the numerous blood conservation techniques and transfusion alternatives now available. A comprehensive monograph on the subject of bloodless surgery along with detailed coverage of risks and benefits of each modality (some modalities are discussed in more detail elsewhere in this issue) is beyond the scope of this article. Accordingly, a brief overview of the history, theory and practice of bloodless surgery is presented, along with the clinical and institutional management requirements.

Aprotinin and deep hypothermic cardiopulmonary bypass with or without circulatory arrest for craniotomy

Deep hypothermic cardiopulmonary bypass with or without circulatory arrest has been used to facilitate the surgical repair of complex cerebrovascular lesions. The advantages of deep hypothermia have been tempered by the occurrence of coagulopathy that is associated with substantial morbidity and mortality. This study analyzed retrospectively the records of 13 patients who underwent cerebrovascular neurosurgery using deep hypothermic cardiopulmonary bypass with or without circulatory arrest during the period 1993 through 1999. All patients received the serine protease inhibitor aprotinin in an effort to avoid the development of a coagulopathy, defined as hemorrhage requiring reoperation. No patients developed postoperative intracranial hemorrhage. There was also no evidence of renal dysfunction, deep venous thrombosis, myocardial infarction, or pulmonary embolism. In conclusion, this study suggests that aprotinin may be beneficial to avoid the coagulopathy that is more likely to occur if deep hypothermic cardiopulmonary bypass with or without circulatory arrest is used for craniotomy without adverse effects on renal function or apparent thrombotic complications.

Practical management of anticoagulation, bleeding and blood product support for cardiac surgery part two: Transfusion issues

We summarise recent advances in transfusion medicine applicable to cardiac surgery and cardiac transplantation. It is important that clinicians know the risks of blood transfusion in Australia. They should also be aware of the different types of transfusion reaction so that there is early recognition and investigation. Blood conservation strategies including acceptance of normovolaemic anaemia in clinically stable patients are important in reducing the requirement for red cell transfusion. Cytomegalovirus (CMV) seronegative blood products are recommended for heart transplant recipients with no evidence of prior CMV infection. Leucodepletion of units of unknown CMV status reduces the risk of CMV infection and are an acceptable alternative when seronegative units are unavailable. Leucodepletion of cellular blood products has been shown to reduce infection rates postoperatively in a large trial involving cardiac surgical patients. Further studies are needed to confirm this promising finding. Irradiation of blood products eliminates the risk of transfusion-associated graft versus host disease. Routine preoperative screening for cold agglutinins is no longer recommended.

A multivariable model for predicting the need for blood transfusion in patients undergoing first-time elective coronary bypass graft surgery

BACKGROUND

The incidence of blood transfusion in coronary artery bypass graft (CABG) surgery remains high. Preoperative identification of those at high risk for requiring blood will allow for the cost-effective use of some blood conservation modalities. Multivariable analysis techniques were used in this study to develop a prediction rule for such a purpose.

STUDY DESIGN AND METHODS

Data were prospectively collected for all patients undergoing elective first-time CABG surgery from January 1997 to September 1998 at a tertiary-care teaching hospital (n = 1007). The prediction rule was developed on the first two-thirds of the sample by using logistic regression methods to examine the relationship of patient demographics, comorbidities, and preoperative Hb with perioperative blood transfusion. The remaining one-third of the sample was used to validate the rule.

RESULTS

The transfusion rate was 29.4 percent. The prediction rule included preoperative Hb (g/dL, OR 0.928, p<0.0001), weight (kg, OR 0.938, p<0.0001), age (years, OR 1.037, p<0.01), and sex (male/female, OR 0.493, p<0.01); receiver operating characteristic = 0.86. When externally validated, the rule had a sensitivity of 82.1 percent and a specificity of 63.6 percent (at a selected probability cutoff).

CONCLUSION

A simple and valid prediction rule is developed for predicting the risk of blood transfusion in patients undergoing first-time elective CABG surgery.

Erythropoietin therapy and preoperative autologous blood donation in children undergoing open heart surgery

We assessed the feasibility and efficacy of subcutaneous erythropoietin alpha (EPO) therapy and preoperative autologous blood donation (ABD) in children undergoing open heart surgery. Thirty-nine children were treated consecutively with EPO (100 U x kg(-1) s.c. three times a week in the 3 weeks preceding the operation and i.v. on the day of surgery) and two ABDs were made (Group 1). As controls to compare transfusion requirements, 39 consecutive age-matched patients who had undergone open heart surgery during the two preceding years were selected (Group 2). In a mean time of 20 (SD 5) days, 96% of scheduled ABDs were performed and only three mild vasovagal reactions were observed. The mean volume of autologous red blood cells (RBC) collected was 6 (1) ml x kg(-1) and the mean volume of autologous RBC produced as a result of EPO therapy before surgery was 7 (3) ml x kg(-1), corresponding to a 28 (11)% increase in circulating RBC volume. The mean volume of autologous RBC collected was not different from that produced [6 (1) vs 7 (3) ml x kg(-1), P=0.4]. Allogenic blood was administered to three out of 39 children in Group 1 (7.7%) and to 24 out of 39 (61.5%) in Group 2. Treatment with subcutaneous EPO increases the amount of autologous blood that can be collected and minimizes allogenic blood exposure in children undergoing open heart surgery.

Desmopressin does not reduce bleeding and transfusion requirements in congenital heart operations

BACKGROUND

Desmopressin (DDAVP) has been evaluated in many randomized clinical trials as a means to reduce blood loss and transfusion of allogeneic blood in cardiac operation requiring cardiopulmonary bypass. Desmopressin reduces blood loss in adult patients with excessive bleeding after cardiac operation. Its usefulness in patients undergoing complex congenital heart repair with cardiopulmonary bypass is unproved.

METHODS

Sixty patients younger than 40 years of age scheduled for complex congenital heart operation (44 redo, 16 primary) were enrolled in this prospective, randomized, double-blind trial. Desmopressin 0.3 microg/kg or placebo was administered 10 minutes after protamine administration. Transfusion requirements and postoperative blood loss were recorded. Differences were analyzed using analysis of variance with a p value of 0.05 or less used to denote statistical significance.

RESULTS

There were no differences in demographic or surgical characteristics between the DDAVP or placebo groups. There was no difference in blood loss and transfusion requirements between the DDAVP and placebo groups. During the intraoperative postinfusion time period, the median blood loss for redo patients was 343 versus 357 mL/m2 for placebo versus DDAVP, respectively, and for primary patients, the median blood loss was 277 versus 228 mL/m2.

CONCLUSIONS

The prophylactic use of DDAVP to reduce excessive bleeding or transfusion requirements in patients undergoing complex congenital heart operations is not warranted.

Blood transfusion support in pediatric cardiovascular surgery

The majority of children who undergo open-heart surgery with cardiopulmonary bypass (CPB) require perioperative blood transfusion. Blood product requirements are affected by factors such as patient age, underlying cardiac disease, complexity of the surgical procedure, and hemostatic alterations induced by CPB. Transfusion support may include the use of whole blood and/or individual blood components with transfusion practices varying widely based on individual preferences and blood product availability. Approaches to limit allogeneic blood exposure include the use of modified ultrafiltration and smaller bypass circuits, preoperative autologous blood donation and intraoperative blood salvage, and adjunctive antifibrinolytic agents. Potential advantages and disadvantages of the different blood products and pharmacological agents must be considered in managing the pediatric cardiac surgery patient.

Impact of innovations on transfusion medicine

The final decade of the last century of the second millennium ad has seen dramatic changes in all aspects of science and health care. In transfusion medicine, the blood supply is the safest it has ever been. Newer refinements and innovations are continuously being researched and implemented to achieve and further enhance safety. Advances in blood conservation, pharmacologic manipulation, engineered blood derivatives, and recombinant growth factors can now provide safer and more effective alternatives to blood transfusions for many patients. This overview highlights selective innovations in transfusion medicine and emphasizes some significant advances that have occurred in blood donor screening, blood component collections and therapy, and laboratory testing. Newer technologies are anticipated that will further enhance the safety of blood and transfusions and potentially augment annually the blood supply on a worldwide basis.

Transfusion-free surgery is a treatment plan for all patients

Due to the increased risks associated with allogenic blood transfusion, blood management in surgical procedures, especially in orthopedic settings, should include reduction of perioperative blood loss. Preoperative nursing assessment will help define patients at increased risk for transfusion. Both nonpharmacologic and pharmacologic techniques can help minimize allogenic transfusion by reducing blood loss. One such method of managing anemia and reducing patient exposure to allogenic transfusion is the perioperative use of recombinant human erythropoietin--erythropoietin alfa--an innovative surgical blood management tool. Increased awareness by perioperative nurses of the use of erythropoietin alfa and patient implications can contribute to the overall blood conservation goal.

Bloodless Pediatric Cardiac Surgery? Deliverance with Erythropoietin

A 2-year-old 11.6 kg boy with congenital heart disease whose parents refused homologous blood products was treated preoperatively with iron and human recombinant erythropoietin for 6 weeks. Surgical repair was performed without exposure to blood products other than human albumin. Treatment with iron and erythropoietin in combination with post-bypass modified ultrafiltration, minimization of hemodilution, reinfusion of residual pump prime, and diuresis may reduce or avoid the need for blood transfusion in acyanotic children undergoing elective cardiac surgery.

Transfusion policies in coronary artery bypass--a nationwide survey in Finland

BACKGROUND

Since the discovery of HIV, minimizing the use of donor blood has become increasingly important in surgical activity. In Finland, however, the use of homologous red blood has grown considerably during the past years. Therefore, we found it necessary to conduct a nationwide survey of transfusion practices in elective surgery. This report deals with transfusions in coronary artery bypass (CABG) operations in all Finish cardiac centres.

METHODS

The study group comprised 804 primary CABG patients operated during a 2-year period. Two reviewers retrospectively examined the data concerning the use of and indications for homologous and autologous blood in the patient charts.

RESULTS

In all, 705 (88%) of patients received homologous blood. The proportions of patients receiving blood components differed between hospitals: from 53 to 99% for red cells, 2 to 22% for fresh frozen plasma and 5 to 49% for platelets. The variation was not caused by diverse patient populations: the mean number of blood component units transfused per patient differed from 1 to 6 between centres-even after adjustment for confounding variables. Multiple blood conservation methods were used in one centre. Nevertheless, homologous blood was administered to 88% of their patients.

CONCLUSIONS

A considerable proportion of CABG patients are transfused with homologous blood in Finland compared to other countries. In addition, the transfusion practices proved highly variable between hospitals and were determined largely by local opinions. This study reveals a clear demand for prospective studies and constructive discussion among anaesthesiologists to establish uniform guidelines for blood use in cardiac surgery.